cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-10 of 10 results.

A277062 Number of primes <= n-th Lucas number.

Original entry on oeis.org

1, 0, 2, 2, 4, 5, 7, 10, 15, 21, 30, 46, 66, 98, 146, 218, 329, 500, 757, 1158, 1766, 2716, 4164, 6420, 9907, 15320, 23760, 36878, 57356, 89288, 139283, 217506, 340059, 532321, 834147, 1308186, 2053958, 3227229, 5075229, 7987852, 12581575, 19831014
Offset: 0

Views

Author

Vincenzo Librandi, Nov 09 2016

Keywords

Crossrefs

Programs

  • Magma
    [#PrimesUpTo(Lucas(n)): n in [0..41]];
  • Maple
    a:= n-> numtheory[pi]((<<0|1>, <1|1>>^n. <<2, 1>>)[1$2]):
    seq(a(n), n=0..35);  # Alois P. Heinz, Nov 09 2016
  • Mathematica
    Table[PrimePi[LucasL[n]], {n, 0, 50}]

Formula

a(n) = A000720(A000032(n)). - Michel Marcus, Jun 10 2024

A052011 Number of primes between successive Fibonacci numbers exclusive.

Original entry on oeis.org

0, 0, 0, 0, 1, 1, 2, 3, 5, 7, 10, 16, 23, 37, 55, 84, 125, 198, 297, 458, 704, 1087, 1673, 2602, 4029, 6263, 9738, 15186, 23704, 36981, 57909, 90550, 142033, 222855, 349862, 549903, 865019, 1361581, 2145191, 3381318, 5334509, 8419527, 13298630
Offset: 1

Views

Author

Patrick De Geest, Nov 15 1999

Keywords

Comments

With the given sequence data, we see that neither endpoint is included, so we count primes p in the open interval F(n)Jeppe Stig Nielsen, Jun 06 2015

Examples

			Between Fib(9)=34 and Fib(10)=55 we find the following primes: 37, 41, 43, 47 and 53 hence a(9)=5.
		

Crossrefs

Cf. A000040, A001605, A005478 (endpoint primes), A010051, A052012, A054782.

Programs

  • Haskell
    a052011 n = a052011_list !! (n-1)
    a052011_list = c 0 0 $ drop 2 a000045_list where
      c x y fs'@(f:fs) | x < f     = c (x+1) (y + a010051 x) fs'
                       | otherwise = y : c (x+1) 0 fs
    -- Reinhard Zumkeller, Dec 18 2011
    
  • Maple
    for n from 1 to 43 do T[n]:= numtheory:-pi(combinat:-fibonacci(n)) od:
    seq(T[n]-T[n-1]-`if`(isprime(combinat:-fibonacci(n)),1,0), n=2..43); # Robert Israel, Jun 08 2015
  • Mathematica
    lst={};Do[p=0;Do[If[PrimeQ[a],p++ ],{a,Fibonacci[n]+1,Fibonacci[n+1]-1}];AppendTo[lst,p],{n,50}];lst (* Vladimir Joseph Stephan Orlovsky, Nov 23 2009 *)
    pbf[n_]:=Module[{fib1=If[PrimeQ[Fibonacci[n+1]],PrimePi[Fibonacci[n+1]-1], PrimePi[ Fibonacci[n+1]]], fib0=If[PrimeQ[Fibonacci[n]], PrimePi[ Fibonacci[n]+1],PrimePi[Fibonacci[n]]]},Max[0,fib1-fib0]]; Array[pbf,50] (* Harvey P. Dale, Mar 01 2012 *)
  • PARI
    a(n)=my(s); forprime(p=fibonacci(n)+1,fibonacci(n+1)-1,s++); s \\ Charles R Greathouse IV, Jun 08 2015

Formula

a(n) = pi(F(n+1)-1) - pi(F(n)) = A000720(A000045(n+1)-1) - A000720(A000045(n)). - Jonathan Vos Post, Mar 08 2010; corrected by Jeppe Stig Nielsen, Jun 06 2015
a(n) ~ phi^(n-1)/(n*sqrt(5)*log(phi)), where phi = (1+sqrt(5))/2 is the golden ratio. - Charles R Greathouse IV, Jun 08 2015
a(n) = A054782(n+1) - A054782(n) - [n+1 in A001605], where [] denotes the Iverson bracket. - Amiram Eldar, Jun 10 2024

A076777 Number of primes between successive Fibonacci numbers inclusive.

Original entry on oeis.org

0, 0, 1, 1, 1, 1, 2, 2, 3, 5, 8, 10, 17, 23, 37, 55, 85, 125, 198, 297, 458, 704, 1088, 1673, 2602, 4029, 6263, 9738, 15187, 23704, 36981, 57909, 90550, 142033, 222855, 349862, 549903, 865019, 1361581, 2145191, 3381318, 5334509, 8419528, 13298630, 21014892, 33227992
Offset: 0

Views

Author

Reinhard Zumkeller, Nov 14 2002

Keywords

Comments

a(n) = #{p prime | A000045(n)A000045(n+1)}.

Examples

			a(10) = 8, as there are 8 primes greater than A000045(10) = 55 and not greater than A000045(10+1) = 89: 59, 61, 67, 71, 73, 79, 83 and 89.
		

Crossrefs

Programs

  • Maple
    with(combinat): with(numtheory): seq(pi(fibonacci(n+1))-pi(fibonacci(n)),n=0..35); # Emeric Deutsch
  • Mathematica
    Table[PrimePi[Fibonacci[k+1]]-PrimePi[Fibonacci[k]],{k,50}] (* Vladimir Joseph Stephan Orlovsky, Nov 30 2010 *)
  • PARI
    A076777(n) = primepi(fibonacci(n+1))-primepi(fibonacci(n))
    A076777(n) = sum(i=fibonacci(n)+1,fibonacci(n+1),isprime(i)) \\ Michael B. Porter, Nov 24 2009

Formula

a(n) = A000720(A000045(n+1)) - A000720(A000045(n)).

Extensions

More terms from Emeric Deutsch, Mar 02 2005
More terms from Amiram Eldar, Oct 07 2021

A138184 Largest prime not exceeding Fibonacci(n) = A000045(n).

Original entry on oeis.org

2, 3, 5, 7, 13, 19, 31, 53, 89, 139, 233, 373, 607, 983, 1597, 2579, 4177, 6763, 10939, 17707, 28657, 46351, 75017, 121379, 196387, 317797, 514229, 832003, 1346249, 2178283, 3524569, 5702867, 9227443, 14930341, 24157811, 39088157, 63245971
Offset: 3

Views

Author

Colm Mulcahy, Mar 04 2008

Keywords

Examples

			a(8) = 19 because 19 is the largest prime not exceeding 21 = A000045(8).
		

Crossrefs

Programs

  • Maple
    A138184 := proc(n) prevprime(combinat[fibonacci](n)+1) ; end: seq(A138184(n),n=3..45) ; # R. J. Mathar, Apr 22 2008
  • Mathematica
    PrimePrev[n_]:=Module[{k=n},While[ !PrimeQ[k],k-- ];k];f[n_]:=Fibonacci[n];lst={};Do[AppendTo[lst,PrimePrev[f[n]]],{n,5!}];lst (* Vladimir Joseph Stephan Orlovsky, Feb 26 2010 *)

Formula

a(n) = A000040(A054782(n)). - R. J. Mathar, Apr 22 2008

Extensions

Edited and extended by R. J. Mathar, Apr 22 2008
Offset changed from 4 to 3 by Harry J. Smith, Jan 02 2009

A082602 Number of primes between successive Fibonacci numbers (including possibly the Fibonacci numbers themselves).

Original entry on oeis.org

0, 1, 2, 2, 2, 2, 3, 3, 5, 8, 11, 17, 24, 37, 55, 85, 126, 198, 297, 458, 704, 1088, 1674, 2602, 4029, 6263, 9738, 15187, 23705, 36981, 57909, 90550, 142033, 222855, 349862, 549903, 865019, 1361581, 2145191, 3381318, 5334509, 8419528, 13298631, 21014892
Offset: 1

Views

Author

Hauke Worpel (hw1(AT)email.com), May 23 2003

Keywords

Examples

			a(10) = 8 because the 10th Fibonacci number is 55, the 11th is 89 and the eight primes between them are 59, 61, 67, 71, 73, 79, 83 and 89.
		

Crossrefs

Programs

  • Magma
    [#PrimesInInterval(Fibonacci(n-1), Fibonacci(n)): n in [2..45]]; // Vincenzo Librandi, Jul 13 2017
  • Mathematica
    lst={};Do[p=0;Do[If[PrimeQ[a],p++ ],{a,Fibonacci[n],Fibonacci[n+1]}];AppendTo[lst,p],{n,50}];lst (* Vladimir Joseph Stephan Orlovsky, Nov 23 2009 *)
  • PARI
    { a(n)= c=0; forprime(N=fibonacci(n),fibonacci(n+1),c=c+1); return(c); }
    

Extensions

Corrected and extended by Rick L. Shepherd, May 26 2003
a(43)-a(44) from Vincenzo Librandi, Jul 13 2017

A277063 Number of primes <= n-th Bell number.

Original entry on oeis.org

0, 0, 1, 3, 6, 15, 46, 151, 570, 2376, 10961, 54941, 297220, 1720725, 10602541, 69176095, 475881437, 3439093081, 26026621617, 205694058211, 1693554793730, 14494778231067, 128711956613875, 1183763037547762, 11258075170582653, 110558809039675629, 1119649516271861536
Offset: 0

Views

Author

Vincenzo Librandi, Nov 10 2016

Keywords

Crossrefs

Programs

  • Magma
    [#PrimesUpTo(Bell(n)): n in [0..14]];
  • Mathematica
    Table[PrimePi[BellB[n]], {n, 0, 20}]

Formula

a(n) = A000720(A000110(n)). - Michel Marcus, Nov 10 2016

Extensions

a(21)-a(26) from Charles R Greathouse IV, Nov 10 2016

A273974 Number of primes <= n-th Catalan number.

Original entry on oeis.org

0, 0, 1, 3, 6, 13, 32, 82, 226, 651, 1939, 5946, 18637, 59736, 194898, 645742, 2167325, 7359262, 25237989, 87325031, 304549332, 1069685013, 3781189896, 13443608964, 48049822995, 172568075048, 622514907195, 2254799747130, 8197867118026, 29909486953987, 109477635390870
Offset: 0

Views

Author

Vincenzo Librandi, Nov 10 2016

Keywords

Crossrefs

Programs

  • Magma
    [#PrimesUpTo(Catalan(n)): n in [0..18]];
  • Mathematica
    Table[PrimePi[CatalanNumber[n]], {n, 0, 27}]

Formula

a(n) = A000720(A000108(n)). - Michel Marcus, Nov 10 2016

Extensions

a(28)-a(30) from Amiram Eldar, Sep 03 2024

A352124 Fibonacci numbers k such that pi(k) is also a Fibonacci number.

Original entry on oeis.org

0, 1, 2, 3, 5, 21, 144
Offset: 1

Views

Author

Marc Kouyoumdjian, Mar 05 2022

Keywords

Comments

No examples larger than pi(144) = 34 are known.
Next term is > Fibonacci(123), if it exists (checked using the b-file in A054782). - Amiram Eldar, Mar 05 2022

Examples

			21 is a term because 21 = Fibonacci(8) and pi(21) = 8 = Fibonacci(6).
		

Crossrefs

Programs

  • Mathematica
    Select[(f = Fibonacci[Join[{0}, Range[2, 20]]]), MemberQ[f, PrimePi[#]] &] (* Amiram Eldar, Mar 05 2022 *)
  • PARI
    isfib(n) = my(k=n^2); k+=(k+1)<<2; issquare(k) || (n>0 && issquare(k-8));
    lista(nn) = for (n=0, nn, if (n!=1, my(k=fibonacci(n)); if (isfib(primepi(k)), print1(k, ", ")))); \\ Michel Marcus, Mar 07 2022

A153385 Number of primes <= Fibonacci(Fibonacci(n)) = pi(A007570(n)).

Original entry on oeis.org

0, 0, 0, 0, 1, 3, 8, 51, 1329, 393790, 5670112879, 43416847208976911
Offset: 0

Views

Author

Harry J. Smith, Dec 25 2008

Keywords

Examples

			a(7) = 51 because Fibonacci(7) = 13, Fibonacci(13) = 233 and there are 51 primes <= 233.
		

Crossrefs

Programs

  • Magma
    [0] cat [#PrimesUpTo(Fibonacci(Fibonacci(n))): n in [1..9]]; // Vincenzo Librandi, Aug 02 2015
  • Mathematica
    PrimePi@# & /@ (Fibonacci@Fibonacci@# & /@ Range@10) (* Robert G. Wilson v, Feb 17 2009 *)
  • XiCalc
    Pi(Fib(Fib(n)));
    

Formula

a(n) = pi(Fibonacci(Fibonacci(n))) = A000720(A007570(n)).
a(n) = A054782(A000045(n)). - Amiram Eldar, Sep 03 2024

Extensions

a(11) calculated using Kim Walisch's primecount and added by Amiram Eldar, Sep 03 2024

A274771 Number of primes <= n-th Carmichael lambda number.

Original entry on oeis.org

0, 0, 1, 1, 2, 1, 3, 1, 3, 2, 4, 1, 5, 3, 2, 2, 6, 3, 7, 2, 3, 4, 8, 1, 8, 5, 7, 3, 9, 2, 10, 4, 4, 6, 5, 3, 11, 7, 5, 2, 12, 3, 13, 4, 5, 8, 14, 2, 13, 8, 6, 5, 15, 7, 8, 3, 7, 9, 16, 2, 17, 10, 3, 6, 5, 4, 18, 6, 8, 5, 19, 3, 20, 11, 8, 7, 10, 5, 21, 2
Offset: 1

Views

Author

Vincenzo Librandi, Nov 11 2016

Keywords

Crossrefs

Programs

  • Magma
    [0] cat [#PrimesUpTo(CarmichaelLambda(n)): n in [2..100]];
  • Maple
    with(numtheory):
    a:= n-> pi(lambda(n)):
    seq(a(n), n=1..100);  # Alois P. Heinz, Nov 11 2016
  • Mathematica
    Table[PrimePi[CarmichaelLambda[n]], {n, 100}]

Formula

a(n) = A000720(A002322(n)). - Michel Marcus, Nov 11 2016
Showing 1-10 of 10 results.